Mooring structure

ABSTRACT

A mooring structure particularly such a structure as will allow a single vessel to be moored thereto in open water and will accommodate surging movements of the vessel. The top of the mooring structure is covered by a downwardly opening shield which allows the structure to be totally submerged and filled with a lubricant such as oil, an oil/water interface being maintained at a level above the lower edge of the shield. A further feature comprises a weight structure resisting the surging movements, the weight structure being in the form of a vessel filled with heavy flowable material.

United States Patent [151 3,675,609 Kohring 51 July 11, 1972 s41 MOORING STRUCTURE 3.455.270 7/1969 Mascenic et al 14/230 [72] Inventor: Walter Kohl-lug, Angle View, Pilgrim's Prima I r Exammer-Trygve M. Bllx Sign West Humble, Dorking, Surrey, En- A"omey Karl w Flocks {22] Filed: March 18, 1971 [57] ABSTRACT Appl. No.: l25,646

Foreign Application Priority Data March I9, 1970 Great Britain ..l3,263/70 U.S. Cl l 14/230, 9/8 P lnt. ..B63b 35/00, B63b 21/52 Field of Search ..l l4/0.5 R, 230, 206 R; 9/8 P A mooring structure particularly such a structure as will allow a single vessel to be moored diereto in open water and will accommodate surging movements of the vessel. The top of the mooring structure is covered by a d'ownwardly opening shield which allows the structure to be totally submerged and filled with a lubricant such as oil, an oil/water interface being maintained at a level above the lower edge of the shield. A further feature comprises a weight structure resisting the surging movements, the weight structure being in the form of a vessel filled with heavy flowable material.

14 Claims, 3 Drawing Figures PATENT'EDJUL 1 1 m2 SHEET 10F 3 ATTORNEY MOORING s'muc'ruas BACKGROUND OF THE INVENTION This invention relates to a structure capable of being used as a mono-mooring, particularly such a structure as will allow a single vessel to be moored thereto in open water and will accommodate surging movements of such a vessel.

In my US. Pat. No. 3,404,654 I have disclosed a structure capable of being used as a mono-mooring comprising a fixed element, a head connected to the fixed element having first and second parts rotatable relative to one another from a rest position about a vertical axis and a weight structure supponed by a plurality of pairs of ropes, the ropes of each pair being respectively connected to the first and second parts so that relative rotation of the parts from the rest position lifts the weight structure by increasing the angle between the ropes of each pair to provide an increasing restoring force tending to move the parts back to the rest position.

The fixed element may incorporate a pipe connected to a sub-line through which a tanker moored to the mono-mooring can load or unload.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improvement to such a mooring structure which enables it to be submerged.

A further object is to provide a mooring structure which is more easily assembled.

According to the present invention the upper portion of the mono-mooring is covered by a downwardly opening shield and cranked mooring arms project below the shield and are connected to the first and second parts, the whole structure being submerged and filled with a lubricant.

Preferably the weight structure is formed by a vessel filled with powder or other flowable material of high specific gravity. This enables the powder or other material to be put into the vessel after installation, for example by blowing.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of mono-mooring in accordance with the invention, will now be described, by way of example only with reference to the accompanying drawings of which:

FIG. I is a vertical section through a submerged mooring structure;

FIG. 2 is a plan view of the structure of FIG. I with the shield and tower removed; and

FIG. 3 is a vertical section through an alternative form of mooring structure.

DETAILED DESCRIPTION Referring to FIGS. 1 and 2 the mono-mooring comprises a hollow annular casing 1 having outer and inner walls 2 and 3, the casing being embedded in a concrete or sand base 12 secured to the sea bed 13 by piles 14. The central part within the casing is filled with concrete 5. A central hollow pillar 6 extends upwardly from the upper surface of the concrete fill and its lower end is joined to the casing wall 3 by a multiplicity of radially extending diaphragm plates 7. A central tubular tower 8 also extends upwardly from the top of the concrete fill 5 within the pillar 6 and accommodates a rigid steel pipe 9, the lower end of which extends through the fill 5 and into the sea bed 13 from which it extends ashore or to an underwater storage tank. A rotatable head 15 is mounted for rotation ts] annular tracks 17A, 178 located respectively on the part 16 and on an upward extension 2A of the casing wall 2, each of the bearings 17 being disposed in radial register with a diaphragm plate 16C and being retained in such position by inner and outer rings. The lateral thrust of the head part 16 is accommodated by two sets of roller bearings 18 rotatably mounted in slots in the inner annular wall 163 of the head part 16 to bear against the second inner head part 20. The second head part 20 comprises an outer annular wall 20A of a diameter having an adequate clearance within the inner wall 168 of the part 16 and a concentric annular inner wall 208 of a diameter to have an adequate clearance over the pillar 6, these walls being joined by a multiplicity of radially extending diaphragm plates 20C the lower ends of which are extended at 208. Each of these diaphragn plates is formed with a pair of spaced apart slots reg'stering with suitable apertures in the inner annular wall 208 to receive a series of upper and lower bearing rollers 22 which bear against the outer surface of the pillar 6. The part 20 is supported axially of the mooring by a series of roller bearings 21 acting between annular tracks 21A carried by the head part 20 and the inner casing wall 3.

The head 15 is covered by a downwardly opening shield 19 which is supported on the pillar 6 and is a leak tight fit around the tower 8. The first head part 16 carries a quadrant shaped downwardly cranked arm 23, the vertical part of which extends downwardly within the shield and projects beyond the shield where it is provided with attachment means for one mooring hawser 24 of a ship, in this case the attachment means is a bollard 25. Similarly a mooring arm 26 attached to the head part 20 has a bollard 28 for a second mooring line 24. As shown in the right hand side of FIG. I the height of the head part 16 is reduced to accommodate the mooring arm 26, this reduction in height extending through an arc of approximately ISO to pen'nit appropriate relative pivotal movement between the parts 16 and 20.

A cylindrical weight structure 30, for example of 250 1200 tons, is disposed with clearance in the annular casing l and is supported by a plurality of pairs 31 of ropes, one rope 31A of each pair having one of its ends anchored to the weight structure and its other end anchored to the extension 16D of one of the diaphragm plates 16C and the other rope 31B having one of its ends anchored to the weight structure and its other end anchored to the extension 201) of one of the diaphragm plates 20C. When the weight structure is in its lowermost position, with the rotatable head parts in the rest position shown in full line in FIG. 2, the ropes of each pair extend in a common radial plane. However, when the rotatable heads pivot away from this rest position through the arcs 29 indicated in FIG. 2, as a result of a pull on the mooring lines 24, the angle between each pair of ropes is increased so that the weight structure is lifted and an increasing restoring force is applied to the parts 16 and 20 tending to move them back to their rest positions. The maximum travel positions of the bollards is shown in broken line in FIG. 2 where the parts in this position have been given the suffix A.

The weight structure 30 is in the form of a container vessel 32 which after installation of the mooring (apart from the shield) is filled with a material 33 having a high specific gravity (greater than 3 and preferably greater than 4) for example powdered barite of 4.2 specific gravity. This material must be flowable so that it can be inserted into the vessel after assembly of the mooring structure from a surface ship for exam ple. It is preferred that the material is particulate and is blown into the vessel through a hose which is then removed. Alternatively the material might be heavy mud. The ropes 31 as well as being anchored to the weight structure are connected to a torus ring 27 which relieves the container vessel 32 of the horizontal forces arising when the angle between the ropes increases.

The support tower 8 extends above the highest water level indicated at 34 and the pipe 9 extending from the top of the tower is connected through a chicksan coupling 36, a further line and a horizontal manifold 37 to a plurality of multiple short ilexible hoses 38 which can be used to load or unload oil or the like to or from a tanker secured to the mooring. The whole mooring is submerged well below (at least four fathoms) the level of the lowest forecasted wave trough, indicated at 41. The mooring structure is filled with a non-corrosive liquid or foam lubricant medium such as oil, the water/oil interface being indicated at 42. The hydrostatic pressure prevents oil escaping below the edge of the shield 19. The oil/water interface is preferably below the level of the bearings 17; in addition these bearings are provided with a shield 43. The oil may for example be chosen to have a specific gravity of 0.855 to 0.885 at the temperatures to which the mooring structure will be subjected. For example for normal temperatures a rust inhibited oil sold by Mobile under the trade name D.T.E. and for temperatures normally below freezing a rust inhibited oil sold by Mobile under the trade name Velocite No. 6.

FIG. 3 shows a mooring structure incorporating a number of modifications, any of which may be applied to the mooring structure of FIGS. 1 and 2. Parts similar to those of FIG. 1 have been given like reference numerals and will not be redescribed. In FIG. 3 the casing walls 2 and 3 are of increased diameters compared with those of HO. 1 and the casing wall 3 has been extended upwardly at 3A to itself form the pillar 6 of FIG. I. A hollow channel 49 has been left in the center of the concrete fill and the pipe 9 which for example is of 4 it. diameter is located in this channel by vibration isolator and pipe supports 50. The tower 8 has been omitted and the upper end of the pipe 9 is connected through a swivel joint 51 to a further pipe 52 extending for example to a buoy on the surface of the sea. The bollards 25 and 28 have been replaced by shackles 53 secured to the bottoms of the mooring arms 23, 26.

The shield 19 is provided with an inner downwardly opening spacing member 54 spaced from the shield 19 by annularly spaced rolled steel joists 55. The member 54 extends downwardly between the shield 19 and the head part 16 and mooring arms 23 and 26 to a level substantially that of the oil/water interface 42. Two lines 56 extend downwardly from the sea surface where they are attached to buoys 57 to within the lower part of the hollow casing 1, one for supplying and the other for extracting the oil or other lubricant medium to or from the mooring structure. By this means the oil can be circulated through the whole structure including within the shield since it passes around the lower edge of the spacing member 54 as indicated.

In this embodiment the weight structure 30 is made up from a number of solid iron blocks 58.

What is claimed is:

l. A mooring structure comprising a fixed element, a rotatable head mounted on the fixed element and having first and second parts rotatable relative to one another from a rest position about a vertical axis, a weight structure supported by a plurality of pairs of ropes. the ropes of each pair being respectively connected to the first and second parts so that relative rotation of the parts from the rest position lifts the weight structure by increasing the angle between the ropes of each pair to provide an increasing restoring force tending to move the parts back to the rest position, a downwardly opening shield covering the rotatable head, and a pair of cranked mooring arms respectively connected to the first and second head parts projecting below the shield and having attachment means for connection to the mooring lines of an object to be moored thereto, the mooring structure being submerged and filled with a lubricant.

2. A structure according to claim 1 in which the mooring arms are quadrant shaped.

3. A mooring according to claim 1 in which the attachment means are shackles secured to the lower ends of the mooring arms.

4. A structure according to claim I in which the outer of the first and second head parts are in the form of rings one outside the other and the outer head part has an arcuate ortion of reduced height to accommodate the mooring arm 0 the inner of the head parts.

5. A structure according to claim 1 including a central rigid pipe extending through the fixed element and above the shield through which pipe a tanker moored to the mooring structure can load or unload.

6. A structure according to claim 5 including a tower extending upwardly from the fixed element to a position above the water surface and accommodating the pipe.

7. A structure according to claim 5 in which the upper end of the pipe is connected by a swivel joint to a further pipe extending to the surface of the water.

8. A structure according to claim 1 including means for circulating the lubricant within the mooring structure.

9. A structure according to claim 8 in which the means for circulating lubricant includes a pair of pipes extending from the inside of the structure to the surface of the water.

10. A structure according to claim 8 in which a spacer member is provided between the shield and the rotatable head around which the lubricant can be circulated.

II. A structure according to claim 1 in which the lubricant is a rust resistant oil.

12. A structure according to claim 1 in which the lubricant has a specific gravity in the range 0.855 to 0.885 at the normal temperatures to which the structure is subjected.

13. A structure according to claim I in which the first and second parts rotate on bearings and in which the oil/water interface is below all the bearings of the outer of the first and second head parts.

14. A structure according to claim 1 in which the weight structure comprises a vessel filled with a flowable material.

i II i i l 

1. A mooring structure comprising a fixed element, a rotatable Head mounted on the fixed element and having first and second parts rotatable relative to one another from a rest position about a vertical axis, a weight structure supported by a plurality of pairs of ropes, the ropes of each pair being respectively connected to the first and second parts so that relative rotation of the parts from the rest position lifts the weight structure by increasing the angle between the ropes of each pair to provide an increasing restoring force tending to move the parts back to the rest position, a downwardly opening shield covering the rotatable head, and a pair of cranked mooring arms respectively connected to the first and second head parts projecting below the shield and having attachment means for connection to the mooring lines of an object to be moored thereto, the mooring structure being submerged and filled with a lubricant.
 2. A structure according to claim 1 in which the mooring arms are quadrant shaped.
 3. A mooring according to claim 1 in which the attachment means are shackles secured to the lower ends of the mooring arms.
 4. A structure according to claim 1 in which the outer of the first and second head parts are in the form of rings one outside the other and the outer head part has an arcuate portion of reduced height to accommodate the mooring arm of the inner of the head parts.
 5. A structure according to claim 1 including a central rigid pipe extending through the fixed element and above the shield through which pipe a tanker moored to the mooring structure can load or unload.
 6. A structure according to claim 5 including a tower extending upwardly from the fixed element to a position above the water surface and accommodating the pipe.
 7. A structure according to claim 5 in which the upper end of the pipe is connected by a swivel joint to a further pipe extending to the surface of the water.
 8. A structure according to claim 1 including means for circulating the lubricant within the mooring structure.
 9. A structure according to claim 8 in which the means for circulating lubricant includes a pair of pipes extending from the inside of the structure to the surface of the water.
 10. A structure according to claim 8 in which a spacer member is provided between the shield and the rotatable head around which the lubricant can be circulated.
 11. A structure according to claim 1 in which the lubricant is a rust resistant oil.
 12. A structure according to claim 1 in which the lubricant has a specific gravity in the range 0.855 to 0.885 at the normal temperatures to which the structure is subjected.
 13. A structure according to claim 1 in which the first and second parts rotate on bearings and in which the oil/water interface is below all the bearings of the outer of the first and second head parts.
 14. A structure according to claim 1 in which the weight structure comprises a vessel filled with a flowable material. 